Basic zinc phosphites

ABSTRACT

Novel basic zinc phosphites are described for use as tannin stain inhibitors which can be represented by the formula;

'United Stan [111 3,917,804

White et al. Nov. 4, 1975 BASIC ZINC PHOSPI-IITES Theoretical Chemistry, Vol. 8.

[73] Assignee: N L Industries, Inc., New York,

[22] Filed: Aug. 6, 1973 [21] Appl. No.: 385,850

Primary Examiner-Oscar R. Vertiz Assistant Examiner-Gregory A. Heller [57] ABSTRACT Novel basic zinc phosphites are described for use as tannin stain inhibitors which can be represented by the formula; [52] US. Cl 423/305; 106/145; 106/15 FP;

106/292 y X ZnO.ZnHPO;, [51] Int. Cl. ..C01B 15/16; COlB 25/26;

C043 C09K /2 wherein X is a number from /2 to 10. [58] Field of Search 423/305; 106/ 14.5, 15 PP, The basic Zinc phosphites are prepared by admixing 106/292 zinc oxide and phosphorous acid in the presence of water.

[56] References Cited OTHER PUBLICATIONS is Claims, No Drawings Mellor: Comprehensive Treatise on Inorganic and BASIC ZINC PHOSPI-IITES BACKGROUND OF THE INVENTION This invention is concerned with novel basic. zinc phosphite pigments and their method of preparation. These pigments are useful as tannin stain inhibitors in water and solvent based coating compositions for. wood surfaces. The pigments also impart-anticorrosive and mildew resistant properties to such coatings.

In the past lead-based pigments such as basic lead silicate complexes anddibasic lead phosphite have been utilized in paints for inhibiting the tannin staining of wood surfaces such as cedar or redwood which are used extensively in roof and siding coverings for homes and other buildings. These pigments act to prevent the bleeding of tannin or other wood colorant from the wood surface through the coating film which would cause streaking and discoloration and thereby destroy the appearance. and quality of the coating. Although the performance of these pigments are highly satisfactory, they suffer from the disadvantage that they are lead-based and therefore ecologically undesirable due to the inherent toxicity of the lead contained therein. As a result industry is constantly seeking new substitutes for lead containing products which are non-toxic and at the same time exhibit the high performance characteristics of the lead products.

In view of the foregoing, itis an object of this invention to provide a substitute for lead-based tannin stain inhibitor pigments.

It is also an object of this invention to provide novel basic zinc phosphites having excellent efficiency as tannin stain inhibitors for wood surface coatings.

It is a further object of this invention to provide a novel process for preparing said basic zinc phosphites.

SUMMARY OF THE INVENTION The basic zinc phosphites of this invention can be represented by the emperical formula;

wherein X is a number from k to 10. The term basic" is well known in the art for describing compounds of lead and is used herein in the same context for describing the basic zinc phosphites of this invention. The basicity of the zinc phosphites is related to the molecular ratio of ZnO to ZnHPO; contained therein. Basicity increases with the ratio; products of high basicity containing higher amounts of ZnO with respect to ZnHPO In the above formula, a molecular ratio of ZnO to ZnHPO of from A to 10 is shown which corresponds to a range of basic zinc phosphites from hemibasic to decabasic. The basic zinc phosphites can be substantially anhydrous; that is containing no bound water of hydration or can be associated with about 1 to 3 moles or more of water of hydration. The presence of water of hydration however is not critical to the performance of the basic zinc phosphites as tannin stain inhibitors. All of the basic zinc phosphite compounds are white solids having slight solubilities in water. When these compositions were tested as tannin stain inhibitors in various latex paint formulations, performance was comparable to a basic lead sulfo-silicate complex.

The process for preparing the basic zinc phosphites of this invention comprises admixing zinc oxide and phosphorous acid in the presence of water to form a basic zinc phosphite wherein the ratio of the number of 2 moles of phosphorous acid to the number of moles of zinc oxide is from l:l.5 to lzl l.

The zinc oxide and phosphorous acid may be admixed in other ways to form the basic zinc phosphites. Forexample, the zinc oxide slurry may be slowly added to an aqueous phosphorus acid solution to achieve substantially the same result as above. It is also possible to slowly add dry zinc oxide to an aqueous phosphorous acid solution using strong agitation.

The crude product forms in the slurry as a white solid which can be recovered for example by filtering. The wet product is then dried to remove excess water. If anhydrous basic zinc phosphites are desired the dried product can be heated to remove all water of hydration. By applying this process for the preparation of the basic zinc phosphites excellent yields are obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic zinc phosphites as prepared in this invention having basicities from 1 to 10 have utility as tannin stain inhibitors for water-based coating compositions such as latex paints. When compared to a basic lead sulfo-silicate complex, the basic zinc phosphites show similar tannin stain inhibitory properties. Normal zinc phosphite, ZnI-IPO and zinc oxide alone are essentially ineffective as tannin stain inhibitors. In addition, physical mixtures of zinc oxide and normal zinc phosphite wherein the molar ratio of zinc oxide to normal zinc phosphite is 3:1 which is, on a mole basis, comparable to the chemical compound, tribasic zinc phosphite, are also ineffective.

The preferred tannin stain inhibitors of this invention are those basic zinc phosphites having basicities of from tribasic to octabasic. A particularly preferred basic zinc phosphite is tribasic zinc phosphite.

In addition to effective inhibition of tannin staining, the basic zinc phosphites of this invention are useful in coating compositions as anti-corrosive pigments and as mildew preventive pigments. In flammable materials such as polyester plastics, the basic zinc phophites impart flame retardancy. Another useful property of many of the basic zinc salts is their ability to absorb high energy ultra-violet radiation. This property makes them suitable for use as ultra-violet screening agents for such UV-sensitive materials as polyethylene, polypropylene and polyvinyl chloride-containing products.

In the method for preparing the instant basic zinc phosphite compositions, the amount of water used in forming the zinc oxide and water slurry is not critical. Generallyv it is preferred to use sufficient water to provide a weight ratio of water to zinc oxide of at than a 3:1 to 8:1. If less than 3:1 ratio is used the slurry tends to become thick and difficult to stir.

Sufficient agitation should be used in forming the slurry in order to achieve a homogeneous dispersion of the zinc oxide. This is preferably accomplished by slowly adding the zinc oxide to water while constantly stirring the slurry until it appears that all the zinc oxide is evenly dispersed. If the zinc oxide is not well dispersed and agglomerates or aggregates of zinc oxide are present, incomplete reaction will take place resulting in low yields and low purities of the basic zinc phosphites formed in the subsequent stages of the process. The zinc oxide slurry may be formed at room temperatures or at elevated temperatures. The zinc oxide used must be substantially pure. Impure zinc oxides contaminated with other metallic oxides will result in reduced 3 yields and reduced purities of the formed basic zinc phosphites. The zinc oxide preferred in this invention is a French process zinc oxide having a purity of approximately 98-99%.

An acid catalyst while not essential, is preferably employed in the process to insure high yields. The catalyst is added to the zinc oxide-water slurry prior to the addition of phosphorous acid.

Among the acid catalysts which may be used are the water soluble organic carboxylic acids containing at least one carboxylate group. The term, water soluble" as used in this invention means water solubility in the zinc oxide-water slurry at the concentrations used for catalyzing the reaction between the zinc oxide and phosphorous acid. In addition, these water soluble organic carboxylic acids may contain other functional groups such as hydroxyl, amino or carbonyl. Among the catalysts useful in this invention are formic acid, acetic acid, propionic acid, butyric acid, maleic acid, citric acid, lactic acid, levulinic acid and the like. lnorganic acids such as nitric acid and sulfamic acid may also be used. Acetic acid is preferred however because it is inexpensive and readily available.

The amount of catalyst preferred is between 0.2% and 1% based on the weight of ZnO in the slurry. Amounts greater than 1% offer no useful function in improving yields and purities of the basic zinc phosphites.

The phosphorous acid admixed with the zinc oxide slurry can be any strength phosphorous acid, either anhydrous or in aqueous solution. it is preferred to use from 50% to 70% aqueous phosphorous acid since it is readily available and can be easily handled.

In order to prepare the basic zinc phosphites of this invention the number of moles of phosphorous acid must be from 1/1.5 to 1/11 the number of moles of zinc oxide. To determine the molar amount of phosphonous acid required to prepare any given basic zinc phosphite the following relationship may be used:

wherein [H PO is the number of moles of phosphorous acid; [ZnO] is the number of moles of zinc oxide; and X is the basicity of the basic zinc phosphite to be prepared. For example, ifit is desired to prepare monobasic zinc phosphite (X=l) using 1 mole of zinc oxide in the slurry, 9% mole of phosphorous acid (100%) would be required. if tetrabasic zinc phosphite (X=4) is desired using 1 mole of zinc oxide, then 1/5 mole of phosphorous acid would be required.

The phosphorous acid should be added slowly to the zinc-oxide-water slurry under constant agitation to prevent agglomeration of the formed basic zinc phosphite with the zinc oxide. Preferably this is accomplished by dropwise acid addition over a period of 45 to minutes.

After all phosphorous acid has been added, the slurry may be heated while stirring to accelerate reaction. Generally heating at to C for from 1 to 5 hours is sufficient to convert all zinc oxide and phosphorous acid to basic zinc phosphite. The slurry may be maintained at room temperatures, however longer reaction times are required.

The basic zinc phosphites form as a white solid which can be recovered by filtering. The product is then dried in an oven at from to 120C. If anhydrous basic zinc phosphites are desired, heating is continued at higher temperatures.

It has been found that yields of basic zinc phosphite of from 96% to 98% are achieved using this process based on the amount of zinc oxide used.

In order to more fully desribe the instant invention the following examples are given:

EXAMPLE 1 This example illustrates the preparation of tribasic zinc phosphite.

(3ZnO ZnHPO 21-1 0) Exactly 209.35g of zinc oxide was stirred into 1500ml of water at room temperature. To the uniform slurry was added 6.25mi of 10% acetic acid. Then 76.28g of 69% phosphorous acid was added dropwise over a period of one hour during which time the temperature rose 27C. The slurry temperature was then raised to 65C and stirring was continued for 3 hours at between 65-70C. The pH of the mixture was 6.65. The reaction mixture was then vacuum filtered and the product was dried for 18 hours at C. The actual yield of product was 269.78g. Theoretical yield was 273.18g. Analysis of the product showed. %Zn (observed), 61.90% Zn (theoretical), 61.4690; %P (observed), 7.24%, %P (theoretical) 7.28%; moles Zn/P (theoretical), 4.00; moles Zn/P (observed) 4.05.

EXAMPLES 2-10 In these examples basic zinc phosphites were prepared using the procedure of Example 1 having basicities ranging from 1 to 2 and 4 to 10. Table 1 below lists the amounts of zinc oxide, water, 10% acetic acid and phosphorous acid used in the preparations.

TABLE 1 Basic Acetic 69% 75.7% 100% Zinc Formula ZnO Water Acid H PO H PO; H PO Zn Zn P P Phosphite (g.) (ml.) (ml.) (g.) (g.) (g.) (Theor) (Obs) (Theor) (Obs) Monobasic ZnO'ZnHPO;"H,O 167.50 750 5.0 111.24 53.42 52.70 12.66 12.80 Dlbasic 2 ZnO'ZnHPOfiH O 315.57 1000 9.5 106.5 56.99 56.90 8.90 9.01 Tetrabasic 4 ZnO'ZHHPOHH O 346.34 2530 10.4 100.96 64.49 63.80 6.11 5.95 Pentabasic 5 ZnO-ZnHPO -H,O 177.19 1000 5.3 39.23 66.68 66.15 5.27 5.67 Hexabasic 6 ZnO'ZnHPOfiH O 180.17 1000 5.4 34.19 67.43 67.70 4.57 4.63 Heptabasic 7 ZnO-ZnHPO "HO 182.47 1000 5.5 30.30 68.81 68.67 4.08 3.83 Octabasic 8 ZnOZnHPOHH O 184.48 1000 5.5 27.21 69.93 70.00 3.68 3.73 Nonabasic 9 ZnOZnHPOHPhO 185.80 800 5.6 24.68 71.54 71.68 3.39 3.06 Decabasic 10 ZnO'ZnHPOHH O 187.04 800 5.6 22.59 72.26 72.08 3.11 2.73

EXAMPLE 11 This example illustrates the performance ofthe basic zinc phosphites of this invention for inhibiting tannin staining of cedar surfaces coated with a latex paint containing the basic zinc phosphites.

In the procedure of a series of acrylic latex paints were formulated containing the basic zinc phosphites prepared in Examples I thru 10. As controls, a basic lead sulfo-silicate complex and a normal zinc phosphite were also formulated in the latex formulations which had the following composition:

A cedar panel was coated with the above acrylic latexes to form side by side vertically painted strips approximately 3% inches wide. The spreading rate was 450 square feet per gallon. An identical latex formulation which contained no tannin stain inhibitor was also applied to the panel as a control. After the latex coatings dried (about 2 hours) a top coat of a commercial acrylic latex-based paint was applied to the dried latex film.

After drying overnight the cedar panel was placed in a Cleveland High Humidity Cabinet for 72 hours. The panels were then visually observed for overall tannin staining of the top coated surfaces. The difference in color of the top coat indicated whether or not cedar staining was effectively inhibited. Theresults are summarized in Table 2 below.

TABLE 2 Inhibition of H Example Tannin Stain Inhibitor Tannin Staining Control Normal zinc phosphite Not effective silicate complex Control None Not effective As the table shows the monobasic zinc phosphite b'egins to show effective tannin stain inhibition whereas normal zinc phosphite is not effective. The tribasic thru octabasic zinc phosphites are as effective as the basic lead sulfo-silicate complex. The nona and decabasic 6 zinc phosphites are also effective but to a moderate degreeas compared to the tribasic thru octabasic zinc phosphites.

EXAMPLE 12 i In this example, an acrylic latex paint modified with an alkyd was formulated containing tribasic zinc phosphite as a tannin stain inhibitor. The same latex was formulated using a basic lead sulfo-silicate complex as a control tannin stain inhibitor. The latex formulations had the following general composition;

, PARTS BY INGREDIENTS WEIGHT Water 292.00 Thickener (Bentone LT-NL Industries, Inc.) 2.00 Dispersant (Tamol 850-Rohm & Haas Co.) 13.00 Potassium Tripolyphosphate 2.00 Anti-Foam Agent (Nopco NXZ-Nopco'Chem. Co.) 2.00 Ethylene Glycol 40.00 Preservative (Super-Ad-It, Tenneco. 1.80 Chemicals Inc.) Titanium Dioxide Pigment 160.00 Acrylic Emulsion'(50% resin solids) 400.00 Alkyd Modified With Metallic Driers 25.00 Coalescent Agent (T ributyl Phosphate) l0.00 Tannin Stain Inhibito? Using the procedure of Example 1 I for coating cedar panels with the latex formulations the top coatings were examined for overall cedar stain inhibition both before and after 72 hours of high humidity testing. The results are summarized in Table 3 below.

TABLE 3 INHIBITION OF TANIN STAINING TANNIN STAIN Before High After 72 hrs in INHIBITOR Humidity High Humidity A. Tribasic'zinc effective effective phosphite B. Basic lead sulfoeffective effective silicate complex As the table shows, tribasic zinc phosphite exhibits comparable tannin stain inhibition compared to the basic lead sulfo-silicate complex in the latex used.

EXAMPLE 13 In this example a polyvinyl acetate copolymer latex paint was formulated containing tribasic zinc phosphite as a tannin stain inhibitor. The same type latex was also formulated containing a basic lead sulfo-silicate complex as a control tannin stain inhibitoroThe latex formulations had the following general composition;

7 Using the procedure of Example ll for coating cedar panels with the latex formulations thedried strips were examined for overall cedar stain inhibition both before and after 72 hours of high humidity testing.

The results are summarized in Table 4 below.

7 TABLE 4 INHIBITION OF TANNIN STAINING TANNIN STAIN Before High After 72 hrs. in INHIBITOR Humidity High Humidity C. Tribasic effective moderately zinc phosphite effective D. Basic lead sulfoeffective effective silicate complex The results show that tribasic zinc phosphite is comparable to the basic lead sulfo-silicate complex.

EXAMPLE 14 Amount of Experiment Type of Catalyst Catalyst(wt.%)

E Formic acid 0.23 F Lactic acid 0.45 G Levulinic acid 0.58 H Nitric acid 0.30 I Propionic acid 0.37 .I Sulfamic acid 0.48

EXAMPLE 15 This example illustrates the preparation of tribasic zinc phosphite wherein the zinc oxide slurry is added to a phosphorous acid solution.

Zinc oxide, 209.35g. was slurried with 765 ml of deionized water and 6.25 ml of acetic acid. A phosphorous acid solution was made-up by adding 75.97 g of 69.28% aqueous phosphorous acid to 600 ml of water. The zinc oxide slurry was then slowly added to the phosphorous acid solution with stirring over a period of 55 minutes. Stirring was continued for 5 hours at between 20C and 88C. The final pH was 6.88. The solids were recovered by filtering and drying at 120C. Yield and analysis of the product was substantially the same as in Example I.

EXAMPLE 16 This example illustrates the preparation of tribasic zinc phosphite wherein no catalyst is employed.

French process zinc oxide, 208.93g. and 1500 ml of water were mixed together at ambient temperature. To this was slowly added 76.28g. of 69% phosphorous acid over a period of one hour. The mixture was then heated to between 65-70C and stirring continued for about 1 hour. The final pH was 6.62. The solids were recovered by vacuum filtering, drying 20 hours at 105C and ham- 8 mer-milling through a 0.02 inch perforated screen. The yield of dried product was 269.7g. Elemental analysis of the product showed:

% Zn; 61.90; %P, 7:26; moles Zn/P, 3.98.

EXAMPLE 1? This example illustrates the ineffectiveness of a physical blend of 3 moles of ZnO and 1 mole of ZnHPO corresponding to the compound tribasic zinc phosphite (3 ZnO.ZnHPO in inhibiting tannin staining of a wood surface.

In this procedure, four acrylic latex paint formulations were prepared each containing different tannin stain inhibitor candidates: the first containing a physical blend of 50.4 parts by weight of normal zinc phosphite and 84.5 parts by weight of zinc oxide (molar ratio of ZnO/ZnHPO was 3/1). The second contained parts by weight of tribasic zinc phosphite as prepared in Example 1.

The latex formulations had the following composition:

The procedure for coating cedar panels as outlined in Example 1 1 was used to test the tannin stain inhibitory characteristics of the candidates. Table 6 below summarizes the results.

TABLE 6 Inhibition of Tannin Stain Inhibitor Candadate Tannin Staining K Physical Blend of 3ZnO/ZnHPO; ineffective L ZnO ineffective M ZnHPO, ineffective N 3 ZnO-ZnHPO,-2H,O effective As the table shows, the physical blend of zinc oxide and zinc phosphite, zinc oxide alone or zinc phosphite alone are ineffective tannin stain inhibitors while the tribasic zinc phosphite of this invention is completely effective.

EXAMPLE 18 This example illustrates the effective tannin stain inhibition of a non-hydrated tribasic zinc phosphite 3 ZnO.ZnHPO The tribasic zinc phosphite of Example 1 was heated in an oven at about 300C for several hours to remove all water of hydration. Using the procedure of Example 1 1. the resulting dehydrated tribasic zinc phosphite was incorporated into the latex paint formulation and tested for tannin stain inhibition on a cedar panel. The effectiveness of tannin stain inhibition was substantially the same as the hydrated tribasic zinc phosphite of Example l.

EXAMPLE 19 Wet analysis Observed Calculated %Zn 48.8 49.14 i

moles Zn/P 1.50 1.50

10 As the results in the table show, corrosion inhibition is imparted to each latex coating containing tribasic zinc phosphite. The controls, on the other hand, show substantial nail head corrosion in almost all cases.

EXAMPLE 2-] Three oleoresinous paints oil-alkyd vehicle were formulated with equal volumes of hemi-basic zinc phosphite, monobasic zinc phosphite and dibasic zinc phosphite respectively. The control paints were made with dibasic lead phosphite, a well known anti-corrosive pigment, and a blank where the'volume of anti-corrosivepigment was replaced with magnesium silicate. The paints were coated on sand blasted clean steel and rusted hot-rolled steel panels. Each paint was applied to the steel panels as single coats and double coats. The control paints were coated on identical steel panels. These panels were then exposed to a marine atmosphere at Ocean City, New Jersey. After 20 months exposure the panels were eval uated for corrosion inhibition using the corrosion ratings'of ASTM D6lO -68; l0=rust; l==l00% rust. The results are noted in Table 8.

TABLE 8 One Coat Two Coats Test Corrosion Inhibitor Clean Steel Rusted Steel Clean Steel Rusted Steel 0 Hemibasic Zinc Phosphite 8 9' 9 9 V Monobasic Zinc Phosphite 7 l 9 6 W Dibasic Zinc Phosphite 7 9 g 9 9 7 X Control (Dibasic lead phosphite) 5 9 9 9 Y Bl k (2] 112] '7t3l 4Q] "At'tcr' eleven months exposure "'After three months exposure 'Afler six months exposure EXAMPLE 2O EXAMPLE 22 This example illustrates the corrosion inhibiting properties of tribasic zinc phosphite when applied to a wood surface containing iron, nail heads flush to the surface.

The latex paint formulations of Examples 1 1, l2 and 13 containing tribasic zinc phosphite as prepared in Example -1 were coated on .white pine beveled siding whichcontained six iron nails driven flush to the surface to the pine boards. As a control the same board was coated side by side with similar latexes which contained no tribasic zinc phosphite. The boards were exposed northand south on vertical test fences outdoors. The condition of the nail heads were observed after 5 days exposure and after.26 days exposure using corrosion ratings .as are, set forth in ASTM D610-68 i.e. l0=no rust; 1=l00% rust. Table 7 below summarizes the results.

One coat of the same paints as in Example 2l wer e applied to No. 100 Bonderized steel panels exposed to salt fog for 300 hours according to ASTM Bl 17-64 and evaluated according to ASTM D714-56; Evaluating Degree of Blistering of Paints.

Table 9 summarizes the results of thesalt fog tests.

Test Y'Blank F( 100 hours) 8M medium amount of very small blisters 8F few very small blisters F failed large blisters The formulation for the test paints of Examples 21 and 22 was as follows:

TABLE 7 INGREDIENT GALLONS 60 Corrosion Inhibitor [.34 E g Titanium Dioxide 5.29 g i 5 Magnesium Silicate 18.44 5 26 5 26 Thickening and suspending Agent 0.27 (Bentone 38-NL Industries, lnc.) Board Latex Formulation days days days days Raw Linseed on 2026 AIR d Resin Solution 28.03 0 Example 11 9 9 9 9 y P Example ll Control 4 4 7 4 i p I ckiss B) Q Example l3 10 10 lo 9 Mineral Spirits medium 25.25 R Example l3 Control 5 4 5 3 Anfhskmnmg Agent 8" s Example i2 9 9 1o 10 T Example [2 Control 5 4 7 5 Total 99.81

11 EXAMPLE 23 This example illustrates the mildew resistant properties of a latex paint containing tribasic zinc phosphite.

The latex paint of Example 1 1 containing the tribasic zinc phosphite as was prepared according to Example 1, was coated on cedar beveled siding and the siding exposed 90 south at Hightstown, N.J. As a control a similar latex was coated on the siding containing no tribasic zinc phosphite.

At the end of 2, 4, and 6 months, the coated siding surface was examined for the presence of mildew growth. Mildew resistance was rated numerically from 1 to 10; a rating of 10 indicated no mildew growth and a rating of indicated substantial mildew growth.

The results are summarized in Table 10.

TABLE Mildew Resistance 90 North 90 South 2 4 2 4 6 Sample mos. mos. mos. mos. mos. mos.

Tribasic zinc phosphite l0 l0 l0 l0 10 10 Control l0 l0 9 10 8 7 As the results indicate tribasic zinc phosphite imparted long term mildew resistance to the coating.

EXAMPLE 24 This example illustrates the flame-retardant properties of tribasic zinc phosphite in a flammable plastic composition.

A flammable polyester composition was prepared by combining the following ingredients:

INGREDIENT Weight Polyester of a polybasic alcohol with saturated and unsaturated polybasic aicds Halogenated polyester 50.0 g Cobalt napthenate 0.2 g Peroxide of methyl ethyl ketone 1.7 g Tribasic zinc phosphite 8.0 g

The oxygen index of the tribasic zinc phosphite-containing polyester composition was 24.6. The same polyester containing no tribasic zinc phosphite had an oxygen index of 21.6. These results show that tribasic zinc phosphite imparts flame retardancy to flammable materials.

We claim:

1. A composition of matter essentially consisting of a basic zinc phosphite represented by the formula; X ZnO.ZnHPO wherein X is a number from k to 10.

2. The composition of claim 1 wherein said basic zinc phosphite contains bound water of hydration.

. Hemibasic zinc phosphite. Dibasic zinc phosphite.

. Tribasic zinc phosphite.

. Tetrabasic zinc phosphite. Pentabasic zinc phosphite. Hexabasic zinc phosphite.

. Heptabasic zinc phosphite.

10. Octabasic zinc phosphite.

11. Nonabasic zinc phosphite.

12. Decabasic zinc phosphite.

13. Monobasic zinc phosphite.

14. A process for preparing basic zinc phosphites comprising admixing zinc oxide and phosphorous acid in the presence of water; the ratio of the number of moles of phosphorous acid to the number of moles of zinc oxide being from 1:1.5 to 1:11.

15. A process for preparing basic zinc phosphites comprising; (a) forming a zinc oxide and water slurry; (b) adding phosphorous acid to said slurry; the ratio of the number of moles of phosphorous acid to the number of moles of zinc oxide being from 121.5 to 1:11 and forming a basic zinc phosphite.

16. The process of claim 15 wherein said zinc oxide slurry contains an acid catalyst selected from the group consisting of water soluble organic carboxylic acids and inorganic acids.

17. A process for preparing basic zinc phosphites comprising; (a) forming a zinc oxide and water slurry; (b) adding at least 0.2% by weight based on the amount of zinc oxide of a water soluble acid catalyst to said slurry to form a catalyzed slurry, said acid catalyst selected from the group consisting of water soluble organic carboxylic acids and inorganic acids; and (c) adding phosphorous acid to said catalyzed slurry, wherein the ratio of the number of moles of phosphorous acid to the number of moles of zinc oxide is from 1:1.5 to 1:11 and forming a basic zinc phosphite.

18. A tannin stain inhibitor represented by the formula; X ZnO.ZnHPO .nH O wherein X is a number from A to 10 and n is a number from 0 to 3. 

1. A COMPOUND OF MATTER ESSENTIALLY CONSISTING OF A BASIC ZINC PHOSPHITE REPRESENTED BY THE FORMULA, X ZNO.ZNHPO3 WHEREN X IS A NUMBER FROM 1/2 TO
 10. 2. The composition of claim 1 wherein said basic zinc phosphite contains bound water of hydration.
 3. Hemibasic zinc phosphite.
 4. Dibasic zinc phosphite.
 5. Tribasic zinc phosphite.
 6. Tetrabasic zinc phosphite.
 7. Pentabasic zinc phosphite.
 8. Hexabasic zinc phosphite.
 9. Heptabasic zinc phosphite.
 10. Octabasic zinc phosphite.
 11. Nonabasic zinc phosphite.
 12. Decabasic zinc phosphite.
 13. Monobasic zinc phosphite.
 14. A process for preparing basic zinc phosphites comprising admixing zinc oxide and phosphorous acid in the presence of water; the ratio of the nuMber of moles of phosphorous acid to the number of moles of zinc oxide being from 1:1.5 to 1:11.
 15. A PROCESS FOR PREPARING BASIC ZINC PHOSPHITES COMPRISING, (A) FORMING A ZINC OXIDE AND WATER SLURRY, (B) ADDING PHOSPHOROUS ACID TO SAID SLURRY, THE RATIO OF THE NUMBER OF MOLES OF PHOSPHOROUS ACID TO THE NUMBER OF MOLES OF ZINC OXIDE BEING FROM 1:15 TO 1:11 AND FORMONG A BASIC ZINC PHOSPHITE.
 16. The process of claim 15 wherein said zinc oxide slurry contains an acid catalyst selected from the group consisting of water soluble organic carboxylic acids and inorganic acids.
 17. A process for preparing basic zinc phosphites comprising; (a) forming a zinc oxide and water slurry; (b) adding at least 0.2% by weight based on the amount of zinc oxide of a water soluble acid catalyst to said slurry to form a catalyzed slurry, said acid catalyst selected from the group consisting of water soluble organic carboxylic acids and inorganic acids; and (c) adding phosphorous acid to said catalyzed slurry, wherein the ratio of the number of moles of phosphorous acid to the number of moles of zinc oxide is from 1:1.5 to 1:11 and forming a basic zinc phosphite.
 18. A TANNIN STAIN INHABITOR REPRESENTED BY THE FORMULA, X ZNO,ZNHPO3,NH2O WHEREIN X IS A NUMBER FROM 1/2 TO 10 AND N IS A NUMBER FROM 0 TO
 3. 